1. Field of the Invention
The present invention relates to a cartridge device to contain a recording medium such as a magnetic tape, particularly to a cartridge device of a recording medium which is equipped with a position detecting mechanism to optically detect the position of the recording medium.
2. Description of Prior Art
To take an example, a record replay system such as a personal computer, an office computer or the like has a backup system connected thereto which is for recording and storing data signals. Into this backup system is placed a data cartridge containing a magnetic tape in its interior so that data signals stored in a memory of the computer body are absorbed and recorded onto the magnetic tape, or that data signals recorded on the magnetic tape are supplied to a memory of the computer body.
A data cartridge 1 to backup data, as shown in FIGS. 1 and 2, is constructed such that its cartridge body is formed by combining a base plate 2 made of a metal plate, for example, an aluminum plate, and a cover member 3 shaped into a square, shallow tray and made of a synthetic resin. Within the data cartridge 1 are placed a supply reel 4a and a take-up reel 4b which are supported by supporting shafts which are not illustrated here and put upright on the base plate 2, in such a way that the reels can freely turn round the shafts.
A magnetic tape 5 supplied from the supply reel 4a passes around a guide pin 6a put upright on one end of the front side of base plate 2, and runs along the internal surface of the front panel 3a of cover member 3, is reflected back by another guide pin 6b put upright on the other end to be wound around the take-up reel 4b. The magnetic tape 5 is supported by a still other guide pin 6c during running.
For the data cartridge 1, on the base plate 2 is put upright a support shaft 7a to which a lid body 7 is jointed in such a way as to be freely rotatable round the shaft. A record replay section 3b provided on the front panel 3a of the cover member 3 is opened and closed by this lid body 7. The record replay section 3b is opened when the data cartridge 1 is placed into a backup system, and a magnetic head on the side of the backup system invades to come into contact with the magnetic tape 5 which runs along the front panel 3a, thereby to execute recording or replaying data signals.
In addition, for the data cartridge 1, on the central part of base plate 2 is put upright a support shaft 8a to which a belt driving roller 8 is joined so as to be freely rotatable round the shaft. A part of the periphery of the belt driving roller 8 faces outward through a window 3c formed on the front panel 3a of cover member 3. When the data cartridge 1 is placed properly into the backup system, the belt driving roller 8 is put into rotation through contact with a driving roller of the backup system.
Around the belt driving roller 8 is wound an endless belt 9. The endless belt 9 not only contacts by pressure with the outer rims of the supply reel 4a and take-up reel 4b, but also passes round a pair of guide rollers 10a and 10b which are put upright on both ends of the rear side of base plate 2 such that it runs endlessly a course in the shape of a trapezoid. The belt driving roller 8 is to drive the supply reel 4a and take-up reel 4b into rotation thereby to allow the magnetic tape 5 to run.
The data cartridge 1 is provided with a false recording prevention mechanism which prevents valuable data signals from being eradicated by accident in association with new data signals being recorded on a magnetic tape 5. This false recording prevention mechanism is constituted by a false recording detection window 3d formed on one side of the front panel 3a of cover member 3, and by a false recording prevention member 11 which connects with the cover member 3 such that it can freely move back and forth between a first position where it opens the false recording detection window 3d and a second position where it closes the false recording detection window 3d.
The data cartridge 1, whenever the false recording prevention member 11 is set at the first position thereby to open the false recording detection window 3d, makes it impossible for a false recording detection means of the data backup system to detect the false recording detection window 3d. Then, the data backup system becomes ready to record data signals onto the magnetic tape 5 because no detection signal is delivered as output from the false recording detection means. Further, the data cartridge 1, whenever the false recording prevention member 11 is set at the second position thereby to close the false recording detection window 3d, makes it possible for the false recording detection means of the data backup system to detect the false recording detection window 3d. In the data backup system, through this operation, a detection signal is delivered as output from the false recording detection means to a recording control section to disable the recording of data signals onto the magnetic tape 5.
The data cartridge 1 is provided with a tape position detecting mechanism which detects a position of the magnetic tape 5, for example, its start end or its terminal end. The tape position detecting mechanism, as shown in FIG. 3, consists of a light receiving slit 2a inscribed on the base plate 2, and a reflective member 12 which is mounted on the base plate 2 as if to close the light receiving slit 2a. The reflective member 12 with a cross-section in the shape of a right-angled triangle is mounted to the base plate 2 such that one of the two sides intersecting each other to form the right angle faces a detection guide slit 2a of base plate 2 and the other faces a position detecting section 3e of cover member 3. The reflective member 12 has a piece of mirror 12a attached on the inner surface of the hypotenuse of the triangle.
When the data cartridge 1 is mounted properly to the backup system, right opposite to the light receiving slit 2a is placed a light emitting element 13 of the backup system. In addition, right opposite to the detection section 3e is placed a light receiving element 14 of the backup system. Accordingly, the data cartridge 1 is so constructed that, a detection light beam which is radiated from the light emitting element 13 and guided through the light receiving slit 2a into the interior, is reflected with a refraction by the mirror piece 12a of the reflective member 12 towards the position detecting section 3e. The detection light beam is guided through the magnetic tape 5 towards the position detecting section 3e, and penetrates this position detecting section 3e to be detected by the light receiving element 14.
Generally, the magnetic tape 5 is made impenetrable to light, but it has transparent sensing tape segments attached at its start and terminal ends. Therefore, while the magnetic tape 5 is running past the position detecting section 3e, the detection light beam is prevented from reaching the light receiving element and no detection of light results. Alternatively, when one sensing tape segment runs past the position detecting section 3e, the detection light beam penetrates this sensing tape segment to be detected by the light receiving element 14. Thus, the data cartridge 1 detects the start or terminal end of a tape.
It should be noted here that the aforementioned tape position detecting mechanism finds the running position of the magnetic tape 5 by detecting, for example, optically active position marks placed on the magnetic tape. Further, the tape position detecting mechanism also acts as a mechanism recognizing the type of data cartridge 1 by reading optically active marks placed on the magnetic tape 5 or on its sensing tape segments which may indicate the recording mode of the tape.
As described above, with this data cartridge 1, the start or terminal end, or the type of a magnetic tape is detected by the light emitting element 13 and the light receiving element 14 which are placed in the backup system such that their axes intersect each other with a right angle. With this data cartridge 1, as the detection light beam radiated from the light emitting element 13 penetrates the position detecting section 3e, at least this position detection section 3e must be made penetrable to light. Accordingly, with this data cartridge 1, generally the cover member 3 has been made of a transparent, polycarbonate resin, and the position detecting section 3e has been formed integrally with the front panel 3a.
The data cartridge 1 with such constitution poses a problem in that it allows its internal structure to be visible from outside through the transparent cover member 3. In addition, as the data cartridges 1 are generally given a uniform appearance, any given cartridge can not be easily distinguished from other same cartridges, which makes the work cumbersome involved in the orderly storage of those cartridges according to their contents. To meet these problems, these cartridges 1 are sometimes provided in a form as shown in FIG. 4: the cover member 3 is made of an opaque synthetic resin which has been conferred an appropriate color, and the light transmitting member 20 made of a transparent synthetic resin is fitted to the position detecting section 3e
Namely, as shown in FIGS. 5 and 6, this data cartridge 1 has a rectangular window 15 on the front panel 3a of the opaque cover member 3 at a position corresponding to the position detecting section 3e. The cover member 3 has, on the inner side of its front panel 3e, holding rib walls 16a and 16b formed along the edges of the window 15 in the direction of height, being integral with the cover member 3. Each of the holding rib walls 16a and 16b has a cross-section in the shape of L, and is formed integrally with the front panel 3a, and hence they form engaging grooves 19a and 19b together with the inner surface of the front panel 3a, which open their mouths along the edges of window 15 in the direction of height.
The holding rib walls 16a and 16b have their respective engaging concavities 17a and 17b semicircular in profile on their surfaces opposite to the front panel 3a as shown in FIG. 8. Further, the top ends of the holding rib walls 16a and 16b are not united with a ceiling 3f as shown in FIG. 10, but form respective notches 18a and 18b there. These notches 18a and 18b, as will be described later, serve as sites by way of which, when a molding die with an undercut structure is used to form the engaging concavities 17a and 17b, the cover member 3 can be neatly removed from the molding die.
The light transmitting member 20 is made of a transparent synthetic resin, and constituted of a base section 20a, and an engaging section 20b which is formed on the back of, and integral with, the base section 20a. The base section 20a has a width sufficiently large to intercept the window 15, and a thickness nearly as large as that of the front panel 3a as shown in FIG. 5. The engaging section 20b is constituted such that, along the parts continuous with the base section 20a and at which the base section 20a has the same width with that of the engaging grooves 19, engaging convex edges 21a and 21b integral with the engaging section 20b protrude along both lateral edges. The engaging section 20b has, on the back surface of engaging convex edges 21a and 21b, engaging convexities 22a and 22b semicircular in profile which correspond in shape with the engaging concavities 17 of holding rib walls 16.
The light transmitting member 20 with above constitution is closely united with the cover member 3 after the engaging convexities 21a and 21b have been jointed with the engaging grooves 19a and 19b respectively, by being pushed upward from the lower edge as shown in FIG. 6. The light transmitting member 20 is kept being united with the cover member 3 after the engaging convexities 22a and 22b have been fitted face to face to the engaging concavities 17a and 17b respectively, as shown in FIG. 7. The light transmitting member 20 is sandwiched from above by the cover member 3 and from below by the base plate 2 after the latter two members have been assembled.
The data cartridge 1 is so constructed as to guide, as shown in FIG. 4, the detection light beam radiated from the light emitting element 13 and reflected with a refraction by the reflective member 12, through the transparent light transmitting member 20 to the light receiving element 14. For the data cartridge 1, as the cover member 3 is made of an opaque synthetic resin, its interior is not accessible to direct vision from outside. Further, with the data cartridge 1, as the engaging convexities 22a and 22b are closely fitted face to face to the engaging concavities 17a and 17b so that the light transmitting member 20 is properly placed with respect to the inner surface of front panel 3a, aberrant shift of the light axis of detection light beam is prevented and the position detection of the magnetic tape 5 is stably achieved.
Incidentally, it happens when the data cartridge 1 is dropped by accident to receive a shock or a strong inward pressure, that the light transmitting member 20 escapes from the cover member 3 in association. Namely, when a strong external force is applied, the holding rib walls 16 holding the engaging convex edges 21a and 21b bend inward to be deformed, the light transmitting member 20, because of losing its supports, falls from the cover member 3 as shown in FIG. 9.
The axis of detection light beam changes as a result of the fall of the light transmitting member 20, and hence it becomes impossible for the data cartridge 1 to detect the position of the magnetic tape 5. Further, for the data cartridge 1, such a fatal problem may happen as that the light transmitting member 20 inflicts damage on the magnetic tape 5 during falling, to make it impossible for the tape to record or replay data signals.
The aforementioned cover member 3 is formed with a molding die consisting of, as shown in FIGS. 11 and 13, a core die 23, a cavity die 24 which is tightly bound to the core die 23 with a parting surface PL as a contact surface, and a sliding die 25 which is contained in the core die 23 and slides laterally. With the molding die, as shown in FIG. 11, when the die components are tightly bound, a cavity is formed therein, and into that cavity a resin melt is injected through a gate 26 prepared on the cavity die 24 until the melt filled the cavity. After the molding die has received a predetermined cooling process, as shown in FIG. 12, the sliding die 25 is slid laterally with respect to the core die 23, and at the same time the core die 23 and cavity die 24 are subjected to a parting operation to achieve parting. The molding die, subsequent to an operation for parting the die components, is subjected to an ejection operation whereby an ejecting pin not illustrated here is put into action to eject the molded cover member 3 from the core die 23 as shown in FIG. 13.
Incidentally, the cover member 3 has, as shown in FIG. 8, the engaging concavity 17 on the inner surface of the holding rib wall 16 which opens its mouth towards the engaging groove 19 forming a closed cavity. This engaging concavity 17 is molded with a convexity 23b semicircular in profile and protruding on a part 23a of the core die 23 which is responsible for the formation of front panel 3a. As the semicircular convexity 23b protrudes normal to the direction in which the core die 23 moves for parting, the molding die of the cover member 3 has an undercut segment. Accordingly, the holding rib walls 16 are detached from the molding die through so-called "forcible removal".
In order for the molding die to allow the forcible removal of the aforementioned holding rib wall 16, on the sliding die 25 is provided a convex segment 25a which is to form the notch 18 on the holding rib wall 16. The convex segment 25a, when the die components are tightly bound together, strikes against the inner surface of the section 23a to form the front panel of cover member 3 as shown in FIG. 11. As seen from above, with the cover member 3, because the holding rib wall 16 has the notch 18 as a result of the convexity 25a of the sliding die 25, the holding rib wall 16 can have a property to bend normal to the direction in which the die is moved during removal. As shown in FIG. 13, by virtue of the existence of the notch 18, the holding rib wall 16 bends to achieve forcible detachment from the semicircular convexity 23b.
With the molding die responsible for the formation of the cover member 3, as described above, forcible removal is applied nearly to the whole length of the holding rib wall 16, and thus a resistance associated with the die removal becomes so large that the holding rib wall 16 may undergo deformation or fracture. Further, with the molding die, during forcible removal, the holding rib wall 16 is scraped to produce resin powder which is left to adhere to the cavity. Such adhered resin may cause production of failed products or breakage of the die. Furthermore, with the cover member 3, the light transmitting member 20 comes to have a holding activity variable depending on how much the holding rib wall 16 is deformed, and may fall in extreme cases.